1. Field of the Invention
The present invention is generally related to micrometers, and more particularly to a dynamic optical micrometer that linearly detects movement over a distance spanning several optical wavelengths.
2. Description of the Prior Art
Present small motion detectors are limited in the distance over which they can be used and the upper dynamic response that they can follow. Physical micrometers, although not limited in distance, typically do not have a fast dynamic response. Small fast motions typically are measured using conventional optical interferometry. In such conventional optical interferometry a beam of light is transmitted upon a moving object and its reflected light is optically interfered with a portion of the original transmitted light. The resulting interference pattern creates a change in optical intensity that varies sinusoidally as a function of the relative state of phase of the light in the two interfering beams. The magnitude of the varying intensity is correlated to a particular position of the object under test with an accuracy that is within a fraction of the wavelength of the light transmitted. However, this conventional approach only allows for the detection of motion over a maximum distance associated with the variation of a single wavelength of the transmitted light. Further motion repeats the described intensity variation and creates ambiguous results.
What is needed, therefore, is an apparatus and a method for dynamically etecting the motion of an object spanning several wavelengths of light.
In addition, it is desirable to produce an indication that is linearly related to the movement of the object.